Toshiba Corp. has developed an LED that emits ultraviolet light with 50 per cent higher efficiency than existing versions, opening the door for LEDs that can shed a light quality similar to a fluorescent lamp. The company hopes to use the technology to commercialize as early as 2010 LED lighting capable of replacing fluorescent lighting.
Today’s UV LEDs are not efficient enough for use in white LEDs, so such devices are now made by coating phosphors on a blue LED. However, because the red color component is weak, red objects look dark when illuminated under these kinds of white LEDs.
As a result, currently available white LEDs are not suited for lighting places like supermarkets and clothing stores.
Toshiba increased the efficiency of its UV LED by placing a thin layer of aluminum nitride between the sapphire substrate and the light-emitting layer of gallium nitride. This reduces boundary defects more than tenfold and helps prevent fissures that lower efficiency.
Toshiba’s prototype LED emits UV light in wavelengths of 383 nanometers. At a current of 20 milliamperes, the device emits light with a brightness of 23 milliwatts, compared with a maximum of 15 milliwatts for conventional UV LEDs.
Coated with green, red and blue phosphors, the UV LED generates white light.
– from tradingmarkets